1. Field of Invention
This invention relates to energy conservation and particularly to the recovery of normally unused heat in hot water lines of a domestic water system.
It is very common for the water system in a typical home to waste ten to twenty-five gallons of hot water each day or as much as about nine thousand gallons per year. It is estimated that one ounce of heating oil or one cubic foot of natural gas or 250 watt-hours of electricity is consumed for every gallon of water heated for domestic consumption. Using energy costs at the end of 1979, conservation of ten to twenty-five gallons of hot water per day could save a typical household about forty dollars to one hundred dollars per year. Skyrocketing energy costs and the need to conserve energy from both the domestic and national perspective are compelling reasons to minimize the waste in heating water.
A gallon of water is trapped in thirty-six feet of three-quarter inch pipe or in sixty-three feet of one-half inch pipe. The heat in trapped water in the length of pipe between the hot water outlet and the water heater tank is typically lost by heat transfer to the pipe and thereafter to the atmosphere and also by the practice of draining water from the pipe until the outlet temperature stabilizes. Hence, both heat and water are wasted in a typical domestic hot water system. What is needed therefore is a technique and device for eliminating the source of heat loss in the hot water lines.
2. Description of the Prior Art
The most common technique for minimizing heat loss in hot water lines is to insulate the lines. While helpful, insulation is not totally effective. Heat is still lost, only more slowly, from trapped water. After an hour or so, depending upon the amount of insulation, most of the usable heat is typically lost.
Systems are known for making hot water instantly available and for inhibiting the freezing of hot water in pipes. One example is U.S. Pat. No. 1,247,374. In that patent, a thermal siphon is employed to force hot water through a bridge conduit into the cold water lines. When there is reverse flow, it is always in a direction forcing the cold water back into its mains. Thus, the teachings of this art urge energy waste in order to accomplish a purpose which wholly fails to address the problems addressed and solved by the present invention.